Die cushion with self-contained guide means



Oct. 28, 1969 D. H. KRAFT 3,474,656

DIE CUSHION WITH SELF-CQNTAINED GUIDE MEANS Filed 001,. 15, 1967 INVENTOR. DERALD H. KRAFT ATTORNEYS.

United States Patent M 3,474,656 DIE CUSHION WITH SELF-CONTAINED GUIDE MEANS Derald Henry Kraft, Canton, Ohio, assignor to E. W. Bliss Company, Canton, Ohio, a corporation of Delaware Filed Oct. 13, 1967, Ser. No. 675,091

Int. Cl. BZlj 13/04 US. Cl. 72-456 12 Claims ABSTRACT OF THE DISCLOSURE A die cushion of a two part construction which incorporates all necessary guides for the pressure pad in a completely self-contained unit thereby obviating the problem of machining guides in the press bed.

This invention relates to die cushions and, more particularly, to an improved guiding arrangement for the cushion.

In carrying on drawing and forming operations on sheet metal and other materials, it has been a usual practice to employ either draw rings or a blank holding pad to hold the metal sheet while the punch engages the metal to draw or form the same to a desired configuration. With both the draw ring and the pad arrangements, pressure pins extend through the bolster plate into engagement with the pressure pad of a die cushion. The die cushion will generally comprise a relatively fixed piston in telescopic arrangement with the reciprocating cylinder pressure pad. The space between the cylindrical pressure pad and the piston is usually provided with hydraulic or pneumatic fluid that supplies the cushioning action. Since it is not unusual that an uneven load would be applied across the pressure pin area, guides are provided on the press frame for the reciprocating pressure pad. In the absence of such guides, the pressure pad is likely to become cocked or bind on the piston making the cushion unresponsive to the actual pressure conditions.

The guides heretofore employed have comprised either a machined recess in the press bed which slidably engages a complementary slide portion on the pressure pad or, the reverse, where a recess on the pressure pad mated with a slide portion on the machine bed. In either case, expensive machining had to be done upon the bed, Also, due to the heavy loads placed upon the presses, the machined surfaces of the bed often wore out and had to be replaced, thus increasing the maintenance cost of these beds.

To remedy the above manufacturing disadvantages, the present invention provides a die cushion having a selfcontained guide in which guideways for supporting the reciprocatory movement of the pressure pad are provided as a built-in part of the die cushion assembly thereby eliminating the necessity of providing machined guideways in the press bed.

In accordance with the present invention, there is pro vided in combination with a drawing press having a bed, a die cushion located in the bed having a pressure pad reciprocating on a piston. The pressure pad has a pressure pin supporting area substantially greater than the area of the piston. A plurality of guideways extend parallel to the reciprocating path of the pressure pad beneath the perimeter of the pressure pin support area. Each guideway comprises a first guide member integral with the pressure pad and reciprocating therewith and a second guide member integral with the piston, the guide members being in mutually sliding engagement during relative reciprocation of the pressure pad and piston.

In accordance with another specific aspect of this invention there is provided in combination with a recipro- 3,474,656 Patented Oct. 28, 1969 cating pressure member of a press, a die cushion with self-contained guide means for supporting the pressure member. The cushion comprises an upper cushion member including a pressure pad, a cylindrical member extending centrally and downwardly from the pressure pad, and a plurality of spaced T-shaped guide pieces extending downwardly around the outer periphery of the pressure pad. The lower cushion member comprises a piston member extending upwardly and centrally from a baseplate and in telescopic arrangement with the upper cylindrical member, and a plurality of rectangular guide pieces connected to and extending upwardly around the outer periphery of the baseplate and being spaced for sliding engagement with the guide pieces of the upper cushion. The telescopic arrangement of the piston and cylinder members provide a cushion zone and the spaced sliding arrangement between the guide pieces of the respective upper and lower cushioned members provide a means for preventing cocking of the upper cushion member during its reciprocatory movement under an uneven load.

In accordance with still another specific aspect of this invention there is provided a die cushion with self-contained guide means in which a stationary baseplate has removable guide pieces bolted thereto for ease of replacement.

Still further in accordance with the present invention there is provided a die cushion unit comprising an upper cylindrical reciprocating member and a lower stationary piston member in which guide pieces fixed to the bottom member have guide faces provided by removable liners thereon.

The primary object of this invention is to provide a die cushion with self-contained guide means which requires no external guiding for proper operation.

Another object of this invention is to provide an improved die cushion in which manufacturing costs are substantially reduced by providing integral guideways built with the die cushion.

Still another object of this invention is to provide a die cushion unit in which the thrust forces due to offcenter loading are effectively counteracted with a minimum amount of guiding structure provided.

These and other objects and advantages will become apparent from the following description when read in connection with the accompanying drawings in which:

FIGURE 1 is a partial elevation view, partly in section, showing the lower portion of a typical press embodymg the guided cushion of this invention;

FIGURE 2 is a horizontal section generally along the plane of line 2-2 of FIGURE 1 showing a section of the die cushion;

FIGURE 3 is a view taken of line 3-3 of FIGURE 1;

FIGURE 4 is an exploded view, partly in section, show- 1ng the upper and lower cushion members of this invention;

FIGURE 5 is a top view, partly in section, of a modi fied guide arrangement; and,

FIGURE 6 is an elevation view, partly in section, of another modified guide arrangement.

Referring now to the drawings wherein the showings are for the purpose of illustrating a preferred embodiment of the invention and not for limiting the same, FIGURE 1 shows a press, generally designated at 10, wherein only the lower portion of the press is shown in limited detail. It will be appreciated that the top portion of the press may be of any conventional design. The press includes a frame 12, uprights 14, and a press bed designated generally at 16. On the press 10 is a bolster plate 18 which sup ports a fixed lower die 20. Surrounding the lower die 20 is a movable die or draw ring 22 supporting the peripheral edges of the sheet metal blank B which is being worked generally along the plane upon by the upper die, not shown. The draw ring 22 is supported by a series of pressure pins 24 that project through holes in the bolster plate with the lower ends of these pins resting on the pressure pad 26 of a die cushion 28 supported in the bed of the press. Only one die cushion 1s illustrated in FIGURE 1 but it will be appreciated that additional cushions may be employed depending on the particular application.

The improved die cushion indicated generally in FIG- URE l at 28 is more specifically shown in FIGURES 2 through 4.

The die cushion 28 generally comprises an upper reciprocating cushion member 34 and a fixed lower cushion member 36. The upper cushion member includes a cylindrical portion 38 which depends from the lower surface of the pressure pad 26 with the pressure pad extending radially outwardly past the cylindrical portion to form an enlarged platform. Radiating from the cylinder 38 are four equally spaced Webs 40, each of which terminates in a guide member 42. Each guide member has a pair of slide faces 44 which are adapted to provide sliding engagement with guides, later to be described, formed on the lower cushion member. The entire upper cushion member is designed to reciprocate in a path parallel to the centerline of the press.

The lower cushion member 36 is composed of a stationary baseplate 46 which is adapted to be bolted down to a support plate 49 through the use of holddown bolts, not shown. Four upstanding rectangular-shaped guide pieces 50 with guide surfaces 52 thereon are provided on the outer periphery of the plate and are so spaced as to mate with the slide faces 44 of the upper cushion member. The guide pieces 50 and guide members 42 thus form guideways parallel to the line of reciprocatory movement of the upper cushion members.

An upstanding piston 54 is formed centrally of the baseplate 46 inwardly of guide pieces 50 and telescopically engages with the cylinder portion 38 of the upper cushion member 34. As will be readily understood, the piston 54 and cylinder 38 define a cushion chamber 55 that provides the desired yielding pressure during operation of the press. Fluid pressure is supplied to chamber 55 by appropriate means such as line 56 connected through the bottom of the support plate and through the baseplate 46. Appropriate sealing means, such as a ring 58 on the piston 54, may be provided to increase the sealing engagement between the piston and cylindrical members and prevent escape of fluid from the cushion chamber.

During operation of the press, the draw ring 22 is suitably positioned in reference to the lower die by providing pneumatic or hydraulic fluid through line 56, thus raising the pad 26 forcing the pressure pins 24 upwardly and thereby positioning the draw ring 22 for press operation. The upper die member, during a working stroke, is drawn downwardly against the work blank B forcing the draw ring 22 downwardly and causing the pressure pins 24 to be urged against the pressure pad 26 of the die cushion 28 thereby causing the upper cushion member 34 to move downward relative to the lower cushion member 36. The movement of member 34 is guided by the sliding engagement of surfaces 44, 52 on guide pieces 42, 50, respectively. After the upper die completes its working stroke and moves upwardly away from the lower die 20, the pressure within the cushion chamber of the die cushion forces cushion member 34 and, thus, the pressure pins 24 upwardly causing the draw ring 22 to act as a stripper plate thereby removing the work blank B from the die 20. The work blank is removed from the lower die 20, a new sheet blank is inserted, and the press is ready for another cycle of operation.

If off center loading should be imposed on the pressure pad 26, there is a tendency of cushion member 34 to cock relative to member 36 and forces will be exerted tending to cause binding of piston 54 in cylinder 38. While such cocking may not render the cushion wholly inoperative,

it could result in the cushion being unresponsive to the actual pressure conditions. The instant invention combats any tendency of the cushion to cock under loads by providing effective guiding for the cushion member 34 on all four sides. Thus, the guide pieces 50 are placed along each side of base 46 and the guides 42 are oriented along the diagonal between pairs of guides 50. It will be appreciated from an inspection of FIGURE 3 wherein the relationship of guides 42 and 50 is clearly illustrated that any tendency of the cushion member 34 to cock or tilt is resisted by the cooperation of these guides. Thus, forces which tend to cock the cushion member 34 about either axis will be met by the direct engagement of surfaces 44 on guides 42 with the surfaces 52 on guides 50. This relationship results from the essentially T-shape of guides 42 and webs 40 when viewed in cross-section whereby the extremities 42a of guides 42 are co-planar with guides 50. This co-planar relationship also prevents any cocking about an axis along any of the webs 40 and also resists any tendency of any of the surfaces 44 to move away from its associated surface 52 on guides 50. Thus, all forces acting on the cushion are directed in the plane of at least some of the guides 50, which is the plane of maximum resistance. The result is an extremely rigid unit.

In the embodiments of FIGURES 2 through 4, the guide pieces 50 are preferably made integral with the baseplate from cast iron since cast iron is quite compatible as a sliding surface. This eliminates wear plates and mounting means. The upper cushion member 26 and the slide faces 44 are also preferably made integrally out of cast iron for sliding engagement with the guide pieces 50 of the lower cushion member.

FIGURES 5 and 6 show modifications of the guide construction. In FIGURE 5, a guide 50 is shown with a removable bronze liner 60 which is connected to the slide piece 50 by appropriate means such as a countersunk screw 62. With this construction, the liner 60 may be readily removed and replaced when the wear becomes excessive. Moreover, the use of replaceable liners reduces manufacturing and maintenance costs. The use of removable liners 60, shown in FIGURE 5, may also be employed in connection with the upper guide pieces 42. i

In FIGURE 6, an alternate means of forming the guide pieces 50" to the baseplate 46" is illustrated with bolts 64 being used to connect the pieces together. Obviously, the guide piece 50" might be connected to the bottom plate 46" through other means such as welding or keying. Also, the piston 54 could be removably attached to the baseplate instead of being integral as shown or it might be welded thereto.

This invention has been described with particular reference to the type of press wherein the lower die is held stationary and a cushion support is provided for a reciprocating draw ring. The invention, however, could just as easily be used to provide a cushion support for other types of die arrangements and it is not intended that the particular die arrangement shown be anything more than illustrative of one such arrangement.

The various aspects of the present invention have been described in connection with certain preferred structural embodiments; however, it is to be appreciated that struc tural changes may be made in these embodiments without departing from the intended spirit and scope of the present invention as defined in the appended claims.

Having thus described my invention, I ciairn:

1. In a press having pressure imparting means supported for reciprowting movement, and a die cushion, the die cushion including a fixed cushion member and a movable cushion member cooperating to define a cushion chamber therebetween, said cushion chamber being adapted to receive a fluid therein, said movable cushion member being supported on said fixed member, said movable cushion member including a pressure pad, the improvement comprising:

a first plurality of spaced guides secured to said movable cushion member for movement therewith;

a second plurality of spaced guides secured to said fixed cushion member;

said guides being in mutual sliding engagement when said movable member moves relative to said fixed member.

2. The improvement of claim 1 wherein each of said movable spaced guides is interposed between a pair of said fixed guides.

3. The improvement of claim 1 wherein said movable guides depend from said pressure pad;

said fixed guides being vertically exending between pairs of said movable guides.

4. The improvement of claim 1 wherein said movable and fixed guides are in engagement at all points around the die cushion.

5. The improvement of claim 1 wherein one of said plurality of guides is each essentially T-shaped in cross section.

6. The improvement of claim 5 wherein the other of said plurality of guides is each in sliding engagement with the extremities of the arms of the T-shaped guides.

7. The improvement of claim 1 wherein said movable cushion member includes a cylinder depending from said pressure pad;

said fixed member including a base;

a piston upstanding on said base and in sliding engagement with said cylinder to define a cushion chamber therebetween;

said first guides depending from said pressure pad and said second guides upstanding on said base;

said first and second guides being in sliding engagement at all points around the periphery of said cylinder.

8. The improvement of claim 7 wherein one of said first and second plurality of guides each comprises a web extending radially in a direction away from said piston,

a guide piece on the radially outer end of each of said webs with said guide pieces extending generally transverse to the plane of said webs;

the other of said plurality of guides being in sliding engagement with the ends of said guide pieces.

9. The improvement of claim 8 wherein said other guides comprise generally fiat pieces disposed at opposed sides of said engaged cylinder and piston.

10. The improvement of claim 1 wherein said guides are located within the vertical plane defined by said pressure pad.

11. The improvement of claim 1 wherein said guides include replaceable liners attached to at least some of said guides.

12. The improvement of claim 1 wherein at least some of said guide pieces are detachable from said die cushion.

References Cited UNITED STATES PATENTS 8/1915 Sonneborn 72-465 2/1941 Glasner 72455 

